Surface modifying treatment of polyester fiber articles to impart soil-release properties thereto

ABSTRACT

SURFACE MODIFIED POLYESTER FIBER ARTICLES WITH SOIL-RELEASE AND ANTI-REDEPSITION PROPERTIES ARE PREPARED FROM UNDRAWN OR DRAWN POLYESTER FIBERS BY WET TREATING THE POLYESTER FIBER TO PROVIDE A COATING THEREON OF COPOLYESTER COMPRISING ABOUT 20 TO 95 PERCENT BY WEIGHT OF POLYOXYALKYLENE UNITS AND THE REMAINDER BEING CRYSTALLIZABLE ESTER UNITS IDENTICAL TO THOSE PRESENT IN THE FIBERS AND, IF TREATING UNDRAWN FIBER, DRAWING THE TREATED FIBER; HEAT TREATING THE COATED DRAWN FIBER TO FIX THE COPOLYESTER TO THE FIBER SURFACE; WASHING THE FIBER TO REMOVE UNFIXED COPOLYESTER; AND DRYING THE FIBER, PREFERABLY BY REHEATING, PRIOR TO FURTHER PROCESSING, SUCH AS BY SPINNING WEAVING, KNITTING, AND THE LIKE, TO FORM OTHER FIBER ARTICLES OF THE INVENTION, WHICH FIBER ACTRICLES HAVE DURABLE SOIL-RELEASE AND ANTI-REDEPOSITION PROPERTIES.

June 8, 1971 RAGE]: EI'AL 3,583,878

SURFACE MODIFYING TREATMENT OF POLYESTER FIBER ARTICLES TO IMPART SOIL-RELEASE PROPERTIES THERETO Filed Sept. 11. l96 2 Sheets-Sheet 1 8 2A 0 0 C02 m m L. as: {Y

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June 8, 1971 G, RAGEP ETAL 3,583,87

SURFACE MODIFYING TREATMENT OF POLYESTER FIBER ARTICLES TO IMPART SOIL-RELEASE PROPERTIES THERETO Filed Sept. 11, 1968 2 Sheets-Sheet 2 STEP WET UNDRAWN POLYESTER FIBER WITH AQUEOUS DISPERSION OF |20% W/W OF COPOLYESTER POLYMER, HAVING 5 '-80% BY WEIGHT OF POLY- A ESTER UNITS IDENTICAL TO THOSE IN FIBER AND 95-20% BY WEIGHT OF POLYOXYALKYLENE UNITS OF 300'I5,000 MOLECULAR WEIGHT, TO

PROVIDE AWET PICKUP ON FIBER OF 5'IOO%.

DRAW WETTED FIBER AT 5o-2e0c TO CRYSTALLIZE FIBER,TO DILUTE AND FIX COPOLYESTER ON 5 Y FIBER SURFACES AND PROVIDE 2xl6 T0 4x16 GRAMS OF POLYOXYALKYLENE UNITS PER cm 2 OF DRAWN FIBER SURFACE.

HEAT DRAWN FIBER TO RELAXATION TEMPERATURES Q TO RELAX FIBER AND FURTHER FIX COPOLY- ESTER TO THE SURFACE.

D WASH RELAXED FIBER SUBSTANTIALLY FREE OF UNFIXED COPOLYESTER.

g OPTIONALLY,ADD FRICTION AGENT.

E REMOVE EXCESS LIQUIDS FROM FIBER.

HEAT AND DRY, FURTHER RELAX AND ANNEAL g FIBER TO REFIX LOOSENED COPOLYESTER FOR FURTHER PROCESSING TO FABRIC.

United States Patent 3,583,878 SURFACE MODIFYING TREATMENT OF POLY- ESTER FIBER ARTICLES TO IMPART SOIL- RELEASE PROPERTIES THERETO Gazie K. Ragep, Box 70, Rte. 4, Durham, N.C. 27702, and Wesley L. Miller, 4415 Gates St., Raleigh, N.C. 27605 Filed Sept. 11, 1968, Ser. No. 758,999 Int. Cl. D06m 15/48, 15/70 US. Cl. 117-7 10 Claims ABSTRACT OF THE DISCLOSURE Surface modified polyester fiber articles with soil-release and anti-redeposition properties are prepared from undrawn or drawn polyester fibers by wet treating the polyester fiber to provide a coating thereon of copolyester comprising about 20 to 95 percent by weight of polyoxyalkylene units and the remainder being crystallizable ester units identical to those present in the fibers and, if treating undrawn fiber, drawing the treated fiber; heat treating the coated drawn fiber to fix the copolyester to the fiber surface; washing the fiber to remove unfixed copolyester; and drying the fiber, preferably by reheating, prior to further processing, such as by spinning, weaving, knitting, and the like, to form other fiber articles of the invention, which fiber articles have durable soil-release and anti-redeposition properties.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to surface modified polyester filament, staple, yarn, and to fabric and other fiber articles formed therefrom having unusual and durable soil-release and anti-redeposition properties and to a process for providing such surface modified fiber articles.

(2) Description of the prior art The art on producing soil-release, surface modified fiber articles is replete with processes used to impart hydrophilic properties to an otherwise hydrophobic polyester surface. Most of these processes involve either chemically etching the fiber surface by hydrolysis, or employ other chemical modifying treatments such as graft polymerization or involve bonding some hydrophilic agent to the polyester surface through chemical reaction or through physical adhesion as a coating thereon.

Among the latter is the process disclosed in French Pat. 1,401,581 which teachings here applicable are included by reference. Therein, the fiber article is wetcoated with a water insoluble copolyester of a polyoxyalkylene glycol and a polyester having ester units chemically identical to, or cocrystallizable with the ester units present in the polyester fiber to be treated. The copolyester is fixed to the fiber surfaces by heat treatment. During this step, it is postulated that the chemically identical units in the copolyester and in the fiber surface cocrystallize to effect the bond. Polyoxyalkylene units of the copolyester thus fixed to the fiber surface impart water wettability thereto and thus soil-release properties.

The French patent further discloses that, to provide adequate bonding according to its process, ratios of from 2:1 to 6:1 in gram mol units of ester units identical to those in the fiber surface to polyoxyalkylene units are needed; and that to impart adequate hydrophilic properties to the fiber, the bonded copolyester should provide from about 1 1O- to about 5x10 grams of polyoxyalkylene units per square centimeter of fiber surface. The copolyesters so employed also should have a relative viscosity, measured using 1 percent by weight of the copolyester in orthochlorophenol at 25 C., of between about 1.1 to 1.5.

However, in practicing the invention as defined in the French patent, several difiiculties have become apparent. Foremost, one finds that when the copolyester is applied to fibers in the recommended concentrations, i.e., to provide about IX 10- to 5 10* grams of polyoxylalkylene units per square centimeter of fiber surface, and then heat fixed, that much of the copolyester is not adequately fixed to withstand further mechanical processing, such as drafting or spinning, and rubs off on processing machinery, there to accumulate to form sticky spots and to cause fiber, sliver, roving or yarn breakage to an intolerable degree. Further, one finds that such treated fiber, as a result of the mechanical removal of large amounts of copolyester, often has inadequate soil-release durability to withstand repeated washings. Moreover, if blend yarns are so treated, such as those formed from polyester fibers with non-polyesters, e.g. cotton, rayon, nylon or other fibers, much of the copolyester is uselessly taken up by the non-polyester fibers, thus being wasted and detracting from both soil-release durability and process economics. A further disadvantage occurs in the use of the process of the French patent on blend yarn fabrics which are to be dyed. Upon washing the dyed fabrics, it is found that there is a tendency for poor dye retention by the copolyester coated non-polyester fiber portions due to the wash non-durability of the coating on such portions and thus removal of the coating therefrom. This undesirable consequence is due to lack of adequate fixing of the copolyester to the non-polyester portions and results in undesirable unevenness and/or changes in fabric color.

SUMMARY OF THE INVENTION It is to remedy the above mentioned difiiculties that the present invention is directed, such remedy being a prime object of the invention.

Thus, it is an object of this invention to provide more economical, durable soil-release polyester articles by surface modification of polyester fibers with a durably fixed copolyester having from about 20 to 95 percent by weight of polyoxyalkylene units.

Another object of this invention is to provide a process for making the aforesaid articles by durably fixing said copolyester to said fiber articles in minute quantities by heating at relaxation temperatures, by wash removal of unfixed copolyester and by drying the fiber prior to me chanical processing.

Other objects and advantages of this invention will be inherent in and apparent from the description which follows.

The objects of this invention are accomplished and the disadvantages found in prior art practices are overcome by the following procedure:

(a) wetting polyester fiber with a liquid dispersion, melt or solution of a substantially water insoluble copolyester containing from about 20 to 95 percent by weight of polyoxyalkylene units and from about to 5 percent by weight of crystallizable polyester units identical to the crystallizable polyester units present in the surface of the polyester fiber in effective amounts suitable for durable fixing as defined in step (b);

(b) if employing undrawn polyester fiber, drawing the undrawn wetted fiber so as to dilute the copolyester on the fiber surface to effective concentrations of from about 2 l0 to 4 l0- grams of polyoxyalkylene units per square centimeter of the drawn surface; and, if employing drawn polyester fiber, by applying as in step (a) the aforesaid effective concentrations to the drawn fiber without further drawing;

(c) heating the drawn fiber to relaxation temperatures therefor to durably heat fix effective quantities of the lee copolyester to the fiber surfaces and to relax drawing strains;

(d) Washing the fiber to substantially remove unfixed copolyester; and

(e) drying the fiber, preferably by reheating, to refix any loosened copolyester to the fiber surfaces.

The polyester filaments so treated are surface modified by the present process to have wash-durable soil-release properties, and may be further processed to form other fiber articles of the invention by conventional means, such as by breaking or cutting filament to form staple; by carding, picking and drafting staple by itself or with non-polyester staple to form sliver and roving; and spinning to form yarn; and by weaving, knitting or other means to form fiber fabric articles of this invention, which also have the presently desired durable soil-release prop erties.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a flow chart schematically showing an embodiment of the instant process using undrawn fiber.

FIG. 2 is a process chart indicating, in greater particularity, process conditions for the embodiment shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process steps of the invention as illustrated by embodiments shown in FIGS. 1 and 2 show the present process as a continuous treatment of undrawn polyester fiber. Alternately, one may treat the drawn fiber continuously or the undrawn or drawn fiber in a batch operation. In the batch treatment of the undrawn fiber, steps A and B may be performed in sequence, step C performed at a later time, and then steps D through G performed at a later time. Intermediate such sequences, the fiber may be stored as in packages.

Steps A and B.Addition of copolyester Following melt spinning, undrawn polyester fiber so formed is in a substantially amorphous state. Treatment or addition of copolyester to the surfaces of the undrawn fiber at this point, according to the invention, can provide important economic and processing advantages over use of drawn fiber. Thus, although application of copolyester to drawn fiber can provide surface modified fiber articles of the invention as shown by the examples, the economic advantages of using undrawn fiber is believed to be so pronounced as to make this a preferred mode of practice.

First, applied copolyester has a better opportunity to interpenetrate the larger portions of amorphous surface of the undrawn fiber than it would the smaller amorphous portions of the more highly crystalline drawn fiber surface, thus to permit yet earlier and more intimate contact of copolyester molecules with fiber surface molecules and thus ultimately provide better fixing or bonding by cocrystallization and/or by formation of solid solutions or other mechanisms, all of which require such close intermolecular contact. Second, initial application of copolyester to the undrawn fiber permits economical use of copolyester in concentrations that are just high enough to insure a uniform coating of particulate copolyester on the fiber surfaces and yet in an amount which will be sufficiently diluted on the drawn fiber surfaces to obviate stickiness problems due to excessive amounts of unfixed polyester. Third, we find that copolyester added to undrawn fiber beneficially acts as a drawing aid and substantially reduces the number of deep dye defects in fabrics produced therewith such as are caused by sticks and used filaments.

In the preferred embodiment, drawing undrawn copolyester coated fiber importantly serves other particular functions desirable for the purposes of this invention. Drawing uniquely and uniformly dilutes the amount of copolyester present per unit surface area of the fiber. In so doing, we believe that copolyester molecules are brought into yet more intimate contact with surface molecules of the fiber thus to permit easier, earlier and more durable fixing of the copolyester to the fiber surfaces. Dilution by drawing also permits most economical use of the copolyester employed by permitting one initially to uniformly coat undrawn fiber with greater concentrations of copolyester than when coating drawn fiber while still using just enough copolyester to insure uniform coating. This amount is then diluted in a uniquely uniform manner through uniformly increasing the fiber surface area and concomitantly uniformly stretching the coating film thereon to a point where the final concentration of copolyester on the surface is less than that which will be inadequately fixed, i.e. less than about 0.5 X 10* g./cm. of polyoxyalkylene units, thus helping to avoid removal of surplus unfixed copolyester during subsequent mechanical processing and the consequent stickiness problems, while still providing just enough copolyester to insure the desired durable bonding and the desired durable soil-release properties.

In general, draw ratios of 2/1 to 10/1 of drawn fiber length to undrawn fiber length may be employed, according to the invention. Either cold or hot drawing may be used, a preferred range for the latter being from about 50 to 260 C. as shown in FIG. 2, and a most preferred range being about to 110 C.

A convenient means for applying the copolyester, as shown in FIG. 1, is to pass fiber through a liquid bath containing the copolyester, either in solution with an innocuous solvent therefor, which liquid also is a very poor solvent for the fiber, or in uniform dispersion in some innocuous liquid which is a very poor solvent for both the copolyester and the fiber, such as water, or a melt of the copolyester. The use of aqueous dispersions are preferred. When a dispersion is used, preferred practice dictates that the copolyester particles be quite small in size for easy and long-lived uniform dispersion to give a more uniform coating on the fiber, and to make great amounts of particle surface area per unit weight of copolyester available for fixing. This permits large numbers of molecules at the copolyester particle surfaces to contact large numbers of fiber surface molecules and thus subsequently to be easily fixed to the fiber surface in great numbers per unit weight of copolyester. We find that copolyester particle sizes of one or less micron in long length are adequate for this purpose.

Suitable concentrations of copolyester, when used in solution or dispersion, may range from about 0.1 to 50 percent by weight with the preferred range being from about 1 to 20 percent by weight as shown in FIG. 2.

To insure the desired uniform coating of the fiber, we have found that fiber wet pick-up, that is to say the weight of copolyester solution, dispersion or melt added to the fiber, may usefully range from about 0.5 to 200 percent depending upon the concentration of copolyester therein and the mol and weight percent and molecular weight of the polyoxyalkylene units present in the copolyester, with a preferred range of about 5 to percent by weight wet pick-up as shown in FIG. 2. The most preferred range for many embodiments is about 10 to 20 percent by weight wet pick-up. Other means also may be used to wet the fiber with copolyester, such as padding, spraying, or melt flowing the copolyester thereon. Bath application is preferred to insure uniform coating.

We have found that, depending upon the denier of the drawn filament fiber used, say 1 to 20 d.p.f., the amounts of applied copolyester which are useful to practice the present invention are those which will provide from about 2 10 to 4X10 grams of polyoxyalkylene units per square centimeter of drawn fiber surface. Less than about 2X10 g./cm. does not seem to afford adequate soil release properties, whereas greater than about 4X10 g./ cm. provides excessive copolyester which is not adequately fixed in heat treatment nor removed by washing and thus provides stickiness problems in mechanical processmg.

The polyoxyalkylene units that are useful herein have the structure of the corresponding polyoxyalkylene glycols used in preparation of the coating copolyesters, defined hereafter, minus a terminal H and a terminal OH,

thus yielding a polyoxyalkylene unit molecular weight of that of the corresponding polyoxyalkylene glycol minus 18. Exemplary of suitable hydrophilic polyoxyalkylene units are those derived from corresponding polyoxyalkylene glycols, such as the glycols of polyoxyethylene, polyoxypropylene, polyoxytrimethylene, polyoxybutylene and their copolymers.

In general, polyoxyalkylene unit weights that are useful herein may range from about 282 to just less than that of the molecular weight of the polyester molecules in the fiber to be treated, with a preferred range of polyoxyalkylene unit molecular weights being from about600 to 15,000 and a most preferred range being from about 2,000 to 6,000.

Step C.Heat fixing Heating drawn polyester fiber is conventional to relax the drawing strains set up therein. However, in the present process, heating the copolyester coated drawn fiber to relaxation temperatures importantly further serves to durably fix the copolyester to the fiber surface. Heating tends to permit the chemically identical polyester units of the copolyester and the fiber to align themselves with regard to one another, and thus to more closely pack upon subsequent cooling. 'It also permits the polyoxyalkylene units to make better contact with the amorphous portions of the fiber surface to more intimately mix or, we believe, better form a solid solution upon subsequent cooling.

To impart these desirable effects, we have found that one may usefully employ fixing temperatures in the range of from about 150 C. to a temperature just below that required to melt the copolyester and fiber crystallites. An exemplary fixing temperature range is from about 200 to 240 C. with heating times ranging from about 0.01 to 360 seconds or above when using a predominantly polyethylene terephthalate fiber coated according to the invention with a polyoxyethylene terephthalate/ polyethylene terephthalate copolyester, the copolyester being formed from a polyoxyethylene glycol having a molecular weight of about 3,000 and the fiber being drawn to a ratio of about 1.

Step D.Washing Critical to present invention is washing the fiber at this point in the process. Washing acts to substantially remove copolyester which was not adequately fixed at step C, and in so doing removes useless unfixed copolyester which otherwise would rub off on processing machinery to produce the troublesome stickiness and breakage problems hereinbefore discussed. Unfixed copolyester molecules may be those with too low a degree of polymerization or formed with too low a mol percent of chemically identical polyester units to that in the fiber to permit adequate fixing by the heat treatment at step C and also those formed with too high a weight percent of hydrophilic units, which latter condition permits the wash liquid to unfix, detach or lift these molecules from the fiber surface despite some previous bonding during heating at step C. According to the present invention, these molecules must now be removed prior to machine processing to avoid stickiness and breakage problems; this is done by washing the fiber substantially free of such molecules.

According to the invention, washing is effected with some liquid, usually polar, which is (l) non-reactive with, i.e. innocuous to, the copolyester and the fiber, (2) in which the parent polyoxyalkylene glycol used to prepare the copolyester is substantially soluble; (3) in which the fiber and copolyester are substantially insoluble under the washing conditions employed; and (4) which should be removable upon drying, say, by volatilization upon reheating the fiber as in step G below. Generally, liquids which tend to swell the fiber to any substantial extent are to be avoided. Exemplary of and outstanding among such suitable liquids are water and aqueous solutions or dispersions.

Although washing may be conducted at ambient room temperatures, for reasons of processing economy it is usually preferable to raise the temperature of the wash liquid to increase the rate of removal of unfixed copolyester. An exemplary temperature range for such heated wash liquids, and more especially for water and aqueous solutions or dispersions, is from about 60 to C.; and generally such preferred temperatures may fall between about 40 C. and a temperature somewhat below the normal boiling point of the wash liquid or the maximum relaxation temperature of the fiber, whichever is lower.

Washing may be conducted by passing the fibers as in a tow through a liquid wash bath, as shown in FIG. 1, or by soaking in such a bath, or by spraying wash liquid onto the fibers or by any other convenient method. However done, washing should be conducted in such manner, by judicious selection of the wash liquid, its quantities, sufiicient wash time and the like, that unfixed excess copolyester is substantially removed from the fiber thereby.

Steps E and F.Optional friction additive For some purposes, end uses or processing conditions, certain of the surface modified polyester fibers produced by this invention may have too low a degree of fiber t0 fiber cohesion or interfiber friction. In such instances it may prove desirable to add a finish to the fiber which would enhance frictional properties during processing. Conveniently, such finish may be added at this point in the instant process, at step E, for example, by passing the washed fiber through a friction finish bath, as shown in FIG. 1, and removing excess liquid as through a pair of nip rolls, or by any other convenient means for finish addition and excess liquid removal.

Typical of the friction additives which may be employed are the aqueous dispersions of insoluble inorganic particulate materials, such as alumina, as shown in FIG. 2. The friction aids should be added, at any event, only in such quantities and be of such a nature which will not be deleterious to either the fiber or the copolyester surfacemodifying coating, nor prevent the copolyester coating from effecting soil release nor adversely affect subsequent fiber processing.

At any event, whether a friction aid is used or not, the washed fiber usually should be nipped free of excess liquids, at step F, either after washing if no friction additive is used, or after addition of the friction aid, to facilitate fiber drying at step G.

Step G.Drying and refixing loosened copolyester Following washing at step D, or addition of a friction aid at step E, the wet fiber is dried, according to the process of this invention, to serve several ends, the most important of which is to dry the fiber and to refix or more permanently bond copolyester molecules to the fiber surface which molecules may have loosened or have been partially debonded therefrom by the wash, and/ or friction additive treatment. Unless so dried and refixed, the loosened copolyester molecules, when substantial in number, would be removed from fiber surfaces during subsequent mechanical processing to cause the aforesaid stickiness and breakage problems and/or undesirably reduce the durability of the soil-release properties of the filament article and fiber articles made therewith below what is obtainable through refixing. Although the drying of the coated, fixed and washed fibers may be conducted at ambient temperatures, it is preferred practice to dry the fiber at elevated temperatures. These temperatures may range from somewhat below that used in step C for fixing up to a temperature just below that required to melt the copolyester and fiber crystallites. As shown in the examples, reheating to dry the fiber tends to improve soilrelease durability. An additional advantage of reheating the fiber at this point is that the fiber is beneficially further relaxed and annealed for subsequent processing into fabric.

An exemplary reheating range, according to the present invention, employable with a polyethylene terephthalate fiber coated with a polyoxyalkylenepolyethylene terephthalate copolyester is from about 110 to 250 C., with a preferred range of about 120 to 200 C. A range of about 155 to 160 C. is most preferred when the polyoxyalkylene content of the copolyester employed is about 60 percent by weight.

Fibers and copolyesters In general, useful fiber-forming crystallizable polyesters for the practice of the present invention are those with no, or a very low degree of, branching groups such as are defined in French Patent 1,401,581. These polyesters form substantially amorphous fibers upon melt spinning and crystallize to a substantial degree upon drawing.

Thus, to practice the present invention, any fiber-forming crystallizable polyester polymer may be used in fiber form, exemplary of which are polyethylene terephthalate, polytetramethylene terephthalate, poly(1,4 bismethylene cyclohexane terephthalate) poly(ethylenenaphthalene-2,4- dicarboxylate) and poly(ethylene-phenoxyethane-4,4'-dicarboxylate), and other such phenoxyalkane polymers as disclosed in US. Pat. 2,465,150; also, the aforesaid polyesters may be used wherein adipate, sebacate, isophthalate, sulfoisophthalate, p-oxybenzoate or p-oxyethoxy-benzoate groups may, Wholly or in part, replace the terephthalate or other carboxylate groups or wherein oxydiethylene or polyoxyethylene groups may, in part, replace the alkylene groups in the aforesaid polyesters. Copolymers of the aforesaid polyesters with one another also may be used. Preferred among the fiber-forming polyesters for instant practice are polyethylene terephthalate, its copolymers with the aforesaid polyesters wherein the polyethylene terephthalate portions represent at least 50 percent by weight of the copolymer and poly(1,4-bismethy1ene cyclohexane terephthalate).

In the practice of the present invention, the copolyesters used to coat the aforesaid polyester fibers contain crystallizable polyester units in percentages of from about 5 to 80 by weight, which units chemically are defined by the crystallizable ester repeating units present in the fiberforming polyester. The remainder of the instant copolyesters contain from about 95 to 20 percent by weight polyoxyalkylene units as hereinbefore defined.

Useful copolyesters may be prepared by esterification or transesterification of appropriate polyoxyalkylene glycols,

8 products. Alternate methods known to the art for providing copolyesters useful to present practice also may be used.

The following examples are used to illustrate the present invention and are not intended to limit it in any Way. Unless otherwise noted, percentages as expressed in the examples indicate percent by weight.

EXAMPLE 1 Preparation of the copolyesters and their use-In the typical preparation of the preferred copolyesters useful in coating a predominantly polyethylene terephthalate fiber, ethylene glycol, polyoxyethylene glycol, dimethyl terephthalate and appropriate transesterification and condensation catalysts are brought to melt temperatures, desirably under a blanket of nitrogen or other inert gas, and heated, desirably with stirring, until a stoichiometric amount of the methanol byproduct is removed, say, under vacuum or by distillation, and the polymerization (DP) has advanced to where the relative viscosity of the copolyester, measured at 25 C. as a 1 percent solution in orthochlorophenol, is above 1.0. Reactant charges and reaction conditions are given in Table 1 which follows.

The copolyesters so provided are meltable, water insoluble and water dispersible white waxy solids. The aforesaid solid products are comminuted to particle sizes of 1 'or less micron and dispersed in water or some innocuous inorganic or polar organic liquid such as in a blender, at about 25 to C., to provide dispersions having a copolyester solids content between about 0.15 and 15 percent. These dispersions are applied to melt spun polyethylene terephthalate filamentous tow by running the tow through a bath of such dispersions so as to provide a wet pick-up by the fibers of between 5 and 100 percent of the fiber. The fibers prior or subsequent to copolyester application are drawn at drawing temperatures of from 50 to 260 C. in intervals of from 1 to 0.05 second per meter of fiber at draw ratios of 2:1 to 10:1, whereby the copolyesters applied prior to drawing are initially fixed to the fibers surfaces. The coated drawn fibers are heat fixed at temperatures of from 150 to 240 C. Subsequent washing frees the fibers of unfixed copolyesters and drying the fibers at 25 to 240 C. produces soil-release articles of this invention. The fiber articles and the woven, knitted and bonded fabrics of the invention processed therefrom have unusually durable soilrelease and anti-redeposition properties, providing for easy release of motor oil, grease, food, clay, and grass stains, even after previous washings.

TABLE I Oopolyester 1A 1B 1C 1D 1E 1F Reaetaut charge:

Monomers:

Ethylene glycol (I):

In grams 103. 3 103. 3 77. 6 55. 8 27. 9 22. 35 In mols 1. 67 1.67 1. 25 0. 0 0. 45 0. 36 Polyethylene glycol (II):

Molecular weight..- 300 750 1, 000 2, 000 4, 000 6, 000 In grams 57. 3 112. 5 140. 0 200. 0 200. 0 240. 0 In mols 0. 19 0. 10 0. 14 0. 1 0. 05 0. 04 Dimethyl terephthalate:

In grams 129. 3 129. 3 97. 1 69. 0 34. 27. 95 015 0. 67 0. 67 0. 5 0. 36 0. 18 0. 144 M01 ratio of (D/(II) 8. 8/1. 0 8. 8/1. 0 8. 84/1. 0 0/1. 0 9/1. 0 9/1. 0 Catalysts, in grams:

Calcium acetatc 0. 1 0. 1 0. 08 0. 05 0. 03 0. 02 Lithium hydride 0. 1 0. 1 0. 08 0. 05 0. 03 0. 02 Reaction conditions:

Pot temperature, O 123-184 -180 144-200 173-220 186-224 235 Heating time, hours 4-8 48 4-8 48 4-8 4-8 EXAMPLE 2 e.g. having a molecular weight from about 300 to 15,000, with appropriate dicarboxylic acids and/ or their diesters, such as terephthalic acid or dimethylterephthalate, and with appropriate glycols having chemical units identical to the repeating units in the fiber, such as polyethylene glycol or ethylene glycol, and then by condensation copolymerization of the alcoholic and/or ester reaction Using the method of Example 1, 6.6 parts by weight of ethylene glycol, 65 to 67 parts by weight of polyoxyethylene glycol of 3000 molecular weight and dimethyl terephthalate in quantities equivalent to 24 to 25 parts by weight of terephthalic acid are transesterified and condensed. The milky white solid copolyester obtained contains about 9 percent polyethylene terephthalate units and is water insoluble and easily comminuted in water to form a dispersion of 1.4 percent solids content of particles of 1 or less micron in size, using a blender.

A tow of 11 d.p.f. undrawn polyethylene terephthalate filaments, each filament having a surface area to weight of about 874 cm. /gram of filament, is run through a bath of the aforesaid dispersion at a rate of about 62 meters/minute to wet coat the filaments. The wet coated filaments are nipped free of superfluous liquid providing a wet pickup of about 20 percent and a copolyester concentration of about 2.86 10- grams of polyoxyalkylene units per square centimeter of filament surface. The tow of wetted filaments is then drawn to a denier of about 2.2 d.p.f., or about 500 percent, at a draw temperature of about 100 C. This drawing step provides for dilution of copolyester on the filaments to a concentration of about 1.3 l grams of polyoxyalkylene units per cm. of filament surface. The drawn coated filaments are heat treated at 200 C. for about 1 second to fix the copolyester to the fiber surfaces and to relax strains set up in drawing. The fixed fibrous tow is passed through a water wash bath containing a small quantity of colloidally dispersed aluminum trioxide as a friction aid, and in so doing is washed substantially free of unfixed copolyester. The washed tow is dried at about 166 C. for about 6 seconds, and then cut to form 1 /2 inch staple fibers. The staple is carded, picked and drafted to form lap rolls and sliver. The polyester sliver is combined with cotton staple sliver, drafted to blended sliver, formed into roving and spun to form 50 percent polyester/50 percent cotton blended yarn, which is woven to fabric greige goods. Swatches of the greige goods are stained with a mixture of blandyblack clay and 30 SAE motor oil and then hand washed with an aqueous solution of the commercial detergent Tide, which is an aryl benzene sulfonate and is marketed by Procter and Gamble Co. Within three minutes the 10 griege goods are freed of all stain. Otherwise similar greige goods, but prepared with polyester fiber not treated by the instant process show no stain removal upon washing. Treated greige goods, washed some and more times with wash cycles, as explained in Table II, show good soil-release after subsequent staining and rewashing.

In manner similar to that described above, a filamentous polyethylene terephthalate undrawn tow is treated with copolyester, drawn, heat fixed and dried, omitting the wash step of the instant process. In processing to staple, the fibers so treated show substantial breakage, the machinery shows substantial accumulation of copolyester in the form of sticky spots at points where the fiber rubs against metal surfaces, and the lap rolls formed therewith show excessive splitting to the extent of being unprocessable.

EXAMPLES 3-13 Using a copolyester prepared as in Example 2, dispersions are prepared and runs are made on drawn and undrawn polyethylene terephthalate fibrous tow under the conditions as shown in Table II.

Examples 3 and 4, and 7 and 8 demonstrate the critical nature of Washing in the instant process with regard to further processing of fiber to fabric.

Examples 5 and 6, and 12 and 13 demonstrate that one may obtain effective soil-release durability when using copolyester dispersions over the range of 0.14 to 14 percent solids and one may process the treated fiber so obtained to fabric with or without a friction aid. With regard to the latter, processing is slower than when a friction aid is used.

Examples 7 to 9 demonstrate the utility of employing drawn tow prior to copolyester treatment in the present process, and the necessary use of a wash step following heat fixing.

Examples 10 and 11 demonstrate the desirability of reheating the washed treated fiber on drying to enhance soil-release durability to a remarkable degree over that obtained by ambient drying.

In all these examples, whether drawn or undrawn tow is employed, the denier of the drawn tow is about 2.2. Nevertheless, according to the invention, tow may be used which after drawing is from about 1 to 20 d.p.f.

TABLE II Example Condition or step 3 4 6 6 7 8 9 10 11 12 13 copolyester bath:

Copolyester content, percent solids 1. 4 1. 4 1. 4 Temperature, in C 25 25 25 Tow residence time, in second 0.2 0.2 0. 1 Tow, UD=undrawn, D=drawn UD UD UD Percent wet pick-up on fiber... 16 16 16 Denier of treated fiber, in d.p.t 11 11 11 Drawing:

Ratio 5. 05 5. 05 5. 05 Temperature, in C 95 95 Residence time in draw zone, in seconds. 0. 55 0.55 0. 55 Heat fixing:

Temperature, in C 205 205 205 205 235 235 235 205 205 200 205 Residence time, in seconds 0. 92 0.92 0.92 0. 92 0. 92 0. 92 0. 92 0. 92 0. 92 1. 8 0. 92 Concentration of copolyester, in grams/cm.

drawn fiberXlO 1. 3 1. 3 13 13 Water wash bath:

Temperature, in C 25 25 68 Residence time, in seconds 0.5 0.5 0. 5 Friction aid bath:

Concentration A1203, percent w./w 0.5 O. 5 Temperature, in C 2 25 Residence time, in seconds 0.2 0. 2 Drying:

Temperature, in 0 166 166 166 166 166 166 166 25 166 166 166 Residence time, in seconds=S, hours 58 58 58 58 58 58 5S 16H 58 10S 58 Processable to staple and fabric yes no yes yes yes no yes yes yes yes yes Wash durability of soil release and an redeposition properties in number of washes oi 1 to 802. greige goods 1 $80 30 80 530 80 5 $80 80 80 1 Washes with a 3 lb. dunmiy load of cotton fabric. Wash cycle: 60 liters of water, grams of Tide detergent 20 min. agitatlon+10 min. soak+4 min. spin+5 min. water rinse agitation-92 min. soak-Hi min. spin dry. Temperature= F.

and which after drawing is coated with copolyester to provide from about 2 10 to 4 l0- grams of polyoxyalkylene units per square centimeter of fiber surface area. The coating concentration to be provided in a particular embodiment is largely dictated by the denier of the fiber to be treated and its chemical composition, the type, weight percent and unit molecular weight of the polyoxyalkylene units used in the copolyester employed, and the end use intended for the treated fiber.

EXAMPLE 14 Using otherwise identical conditions and materials as described in Example 3, a filamentous tow of a copolymer of 90 percent of polyethylene terephthalate and percent of polyethylene isophthalate is treated and processed satisfactorily to fabric. Durability tests show excellent soilrelease properties after 80 washings.

EXAMPLE 15 Using otherwise identical conditions and materials as described in Example 3, a filamentous tow of a 30/70 blend of cis/trans poly(l,4-bismethylene cyclohexane terephthalate) is treated with a 1.4 percent dispersion in water of a copolyester containing 50 percent of 1,4-bismethylene cyclohexane terephthalate and 50 percent of polyoxyethylene terephthalate having a unit weight of 4,000. The treated tow processes to greige goods without processing difiiculties. The soil release durability tests show good soil release even after 80 wash cycles, with excellent soil anti-redeposition.

EXAMPLE 16 A 1.4 percent aqueous copolyester dispersion is formed with copolyester 1B of Example 1 wherein about 95 percent of the particles have sizes in excess of 1 micron in long length, i.e. the longest length of the particle. This dispersion is used according to the conditions and with the materials of Example 3. The treated fiber is processed to fabric with no difliculty; however, the fabric shows soil-release durability of only 2 wash cycles.

EXAMPLE 17 Two swatches of greige goods are prepared from 50/50 cotton/polyethylene terephthalate blend yarns, one using the coated polyester fiber prepared according to the process of this invention as described in Example 2 above and the other using the materials of Example 2 but employing the process as described in Example 13 of French Pat. 1,401,581 (treatment of a blend fabric with an aqueous copolyester dispersion to deposit 3 percent by weight of solids onto the fabric which is then heated in a stretching frame to 180 C. for 30 seconds). The two swatches are dyed with a conventional disperse dye used in the dyeing of such blend fabrics. The swatch prepared as in Example 2 above dyes well and evenly, and after a number of successive washings, such as 10 washings, remains even in coloration and intensity; the swatch prepared according to the teaching of French Pat. 1,401,581 is of uneven and diminished coloration after 10 washings.

It is to be understood that changes and variations may be made from the foregoing embodiments of the present invention without departing from the spirit and scope thereof as defined in the appended claims.

What is claimed is:

1. A process for treating polyester fiber to impart soilrelease properties thereto prior to mechanical processing into textile articles comprising the steps of:

(a) coating said fiber with a copolyester comprising about 5 to 80 percent by weight of polyester units chemically identical to those of said fiber and about 95 to 20 percent by weight of polyester units derived from a polyoxyalkylene glycol, said copolyester being used in an amount sufficient to coat the polyester fiber and provide polyoxyalkylene units in the range of 12 from about 2 10 to 4 10- grams of p alkylene units per square centimeter of fiber surface;

(b) heating said coated fiber at a temperature and for a time sufiicient to bond said copolyester to said fiber;

(c) washing said fiber with a liquid which is non-reactive with the treated fiber whereby said fiber is substantially freed of any unbonded copolyester;

(d) drying said fiber; and

(e) thereafter mechanically processing said treated fiber into textile articles.

2. A process as defined in claim 1 wherein the polyester fiber treated has been previously drawn.

3. A process as defined in claim 1 wherein the polyester fiber treated is undrawn fiber and wherein said fiber is drawn at a ratio of about 2 to 10 times its original length prior to heat bonding the copolyester to said fiber surface.

4. A process as defined in claim 1 wherein the polyester fiber comprises polyethylene terephthalate.

5. A process as defined in claim 1 wherein the polyester fiber comprises poly(1,4-bismethylene cyclohexane terephthalate) 6. A process for treating polyester fiber to impart soilrelease properties thereto prior to mechanical processing 1nto textile articles comprising the steps of:

(a) treating said fiber with an aqueous dispersion comprising a copolyester wherein the copolyester particle sizes are one micron or less in length and comprising about 5 to percent by weight of polyester units chemically identical to those of said fiber and about to 20 percent by weight of polyester units derived from a polyoxyalkylene glycol, said copolyester being present in the dispersion in an amount sutficient to coat the polyester fiber and provide polyoxyalkylene units in the range of from about 2 10 to 4 10- grams of polyoxyalkylene units per square centimeter of fiber surface;

(b) heating said coated fiber at a temperature of from about C. to a temperature just below that required to melt the copolyester and fiber crystallites gar a time sufiicient to bond said copolyester to said (c) washing said fiber with a liquid which is non-reactive to the treated fiber whereby said fiber is substantially freed of any unbonded copolyester;

(d) drying said fiber Within a temperature range of from ambient temperature to a temperature just below that required to melt the copolyester and fiber crystallites; and

(e) thereafter mechanically processing said treated fiber into textile articles.

7. A process as defined in claim 6 wherein the polyester fiber treated has been previously drawn.

8. A process as defined in claim 6 wherein the polyester fiber treated is undrawn fiber and wherein said fiber 1s drawn at a ratio of about 2 to 10 times its original length prior to heat bonding the copolyester to said fiber surface.

9. A process as defined in claim 6 wherein the polyester fiber comprises polyethylene terephthalate.

10. A process as defined in claim 6 wherein the polyester fiber comprises poly(1,4-bismethylene cyclohexane terephthalate).

References Cited UNITED STATES PATENTS 3,136,655 6/1964 Wolinski 117138.8F 3,416,952 12/1968 McIntyre et al. 117138.8F 3,464,852 9/1969 Caldwell et al. 1l7--l38.8F

WILLIAM D. MARTIN, Primary Examiner J. E. MILLER, Assistant Examiner US. 01. X.R. 117-138.8F, 161K 

